(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Handbook Of Chemical Engineering - I"

PYROMETRY
TABLE 9.—CALIBRATION DATA or REPRESENTATIVE COUPLES Cold-junction temperature = 0°C. electromotive force in millivolts
443
Engelhard "Le Chatelier"		Johnson-Matthey "ke Chatelier"		Copper-Constantan		Iron-Constantan			Chromel-Alumel	
Electromotive force	Temperature, degrees Cen tigrade	Electromotive force	Temperature, degrees Centigrade	Electromotive force	Temperature, degrees Centigrade	Electromotive force	Temperature, degrees Centigrade		Electromotive force	Temperature, degrees Centigrade
0	0	0	0	0	0	0	0	0	0	0
1	147	1	146	1	25	5	105	95	5	122
2	2 5	2	260	2	49	10	204	186	10	243
3	374	3	364	3	72	15	299	277	15	363
4	478	4	461	4	94	20	392	367	20	482
5	578	5	553	5	115	25	483	457	25	601
6	675	5	641	6	136	30	574	546	30	721
7	770	7	725	7	156	35	662	632	35	844
8	861	8	806	8	175	40	749	713	40	970
9	950	9	884	9	194	45	836	792	45	1,100
10	1,037	10	959	10	213	50	924	871		
11	1,122	11	1,032	11	232	55	1,011	950		
12	1,206	12	1,103	12	250	60		1,030		
13	1,290	13	1,173	13	268		B	L		
14 15	1 , 373 1,455	14 15	1,242 1,311	14 15	285 302	B   represents   mean   calibration   by Bureau   of    Standards   of   Iron-con-				
		16	1,379	16	319	stantan couples from all sources.    L				
		17	1,447	17	336	represents mean calibration of Leeds				
				18	353	and       Northrup's      Iron-constantan				
						couple.				
General Theory of Optical and Radiation Pyrometry.—The temperature of a material may be obtained from a measurement of the intensity of the radiant energy it emits. This measurement may refer to the radiation of all wave lengths emitted by the material, or if the material is glowing, the measurement may refer to the visible light emitted, or to the radiation in a very restricted portion of the visible spectrum. However, in general, the intensity of radiation depends not ulonc upon the temperature of the source, but also upon the particular material constituting the source. Thus glowing carbon appears to the eye about three times as bright as glowing platinum when both are at the same temperature. This is technically expressed by the statement that the emissive power or emissivity of carbon is about three times that of platinum. A material having the highest theoretically possible emissivity is known as a "black body." In general it is customary to assign a numerical value of 1 to the emissivity of a black body. Hence all other materials have an emissivity less than 1. A black body is experimentally realized by uniformly heating a hollow enclosure and observing the radiation coming from a small opening in the wall. The intensity of radiation emitted from this opening depends only on the temperature of the walls. It does not depend upon the material of which the walls are constructed. If E = the emissivity of any non-transparent material and R = its reflection coefficient it can be shown that E -{- R ~ 1. If a material having an emissivity of say 0.40, and hence a reflection coefficient of 0.60, is placed inside a black body it becomes indistinguishable from its surroundings. The total intensity of radiation leaving the material is the same as that emitted by the black body. Thus while the